A steam generating unit, such as a boiler, is well known. Such a steam generating unit is used in a steam system iron to generate pressurized steam which is applied to a fabric of a garment to remove creases from the fabric.
A steam system iron comprises a base unit in which a steam generating unit is disposed and a separate steam iron head. The steam iron head is held by a user and has a sole plate which is pressed against the fabric of a garment. A flexible hose extends between the base unit and the steam iron head, and pressurized steam generated by the steam generating unit in the base unit flows along the hose to the steam iron head. The pressurized steam is then discharged from the steam iron head through holes in the sole plate.
A conventional steam generating unit comprises a housing in which a water heating chamber is defined. Water is fed into the water heating chamber through a water inlet and a heating element is operated to heat the water in the water heating chamber. The water is heated in the water heating chamber to generate steam at a high pressure, which is then exhausted from the water heating chamber through a steam outlet into the flexible hose.
When steam is generated in the water heating chamber a residual amount of water is retained in the water heating chamber. A problem with known steam generating units is that the concentration of dissolved salts and solids in the residual water increases during prolonged use of the steam generating unit. Therefore, scales and solid particles are formed in the water when water fed into the water heating chamber is heated and converted into steam due to these dissolved solids in the water. As further water is fed into the water heating chamber and converted into steam, the amount of precipitated scales and solid particles, and the concentration of the dissolved solids in the residual water increases. This is known to result in foaming of the residual water, and may lead to water and scales being drawn through the steam outlet along with the steam to the steam iron head, resulting in scale formation and accumulation in the steam iron head and staining of the garment and sole plate. Furthermore, the high concentration of dissolved solids in the water heating chamber leads to increased corrosion of the steam system iron components, such as the water heating chamber and the heating element, as well as reduced operational efficiency and a reduced life of the steam system iron.
In an attempt to mitigate the above problems it is known to rinse the water heating chamber at regular intervals with water in an attempt to remove the residual water having a high concentration of dissolved solids, and the precipitated solids from the water heating chamber. Such a rinsing operation is performed by feeding a quantity of water into the water heating chamber through an upper opening and then manually emptying the diluted water by shaking the base unit and turning the base unit upside down so that the diluted water flows from the upper opening. However, this operation is difficult for a user to perform due to the weight and size of the base unit.
Another known approach is to feed a predetermined quantity of water into the water heating chamber to dilute the residual water and to drain this diluted water from the water heating chamber. The diluted water is drained to a storage tank for subsequent disposal by a user. Such an operation may be performed automatically by a control unit. However, a problem with this arrangement is that the precipitated scales and particles are known to prevent a drain valve from sealing properly. Therefore, a filter is generally used to prevent scales and particles flowing through the drain valve, and so these scales and particles are retained in the water heating chamber.
Therefore, a problem with the above rinsing arrangements is that the precipitated scales and particles still build up in the water heating chamber in between rinsing operations and are difficult to remove from the water heating chamber.